U.S. patent application number 13/909036 was filed with the patent office on 2013-10-24 for method and apparatus for making skirtless seals.
This patent application is currently assigned to CMD CORPORATION. The applicant listed for this patent is Paul A. Selle. Invention is credited to Paul A. Selle.
Application Number | 20130281278 13/909036 |
Document ID | / |
Family ID | 49380635 |
Filed Date | 2013-10-24 |
United States Patent
Application |
20130281278 |
Kind Code |
A1 |
Selle; Paul A. |
October 24, 2013 |
Method and Apparatus For Making Skirtless Seals
Abstract
A machine and method for converting film into bags or other
articles includes a web traveling from an input section to a rotary
drum, to an output section. The rotary drum includes at least one
seal bar with a sealing zone and a weakening zone, or it can
include or at least one sealing die that extends in the machine
direction. The single sealing zone or sealing die may be a heated
perforator, and may include a heating wire. The heating wire may be
an NiCr wire stitched into the heater, and be disposed on a cap or
on the seal bar. The weakening zone may create a line of weakness
that is uniform or varies in intensity. The sealing zone may
include temperature zones, cartridge heaters, cooling air, or
heated air, or a source of ultrasonic, microwave or radiative
energy.
Inventors: |
Selle; Paul A.; (Appleton,
WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Selle; Paul A. |
Appleton |
WI |
US |
|
|
Assignee: |
CMD CORPORATION
Appleton
WI
|
Family ID: |
49380635 |
Appl. No.: |
13/909036 |
Filed: |
June 3, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13042870 |
Mar 8, 2011 |
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13909036 |
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12253724 |
Oct 17, 2008 |
8029428 |
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13042870 |
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12159979 |
Jul 2, 2008 |
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12253724 |
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12145913 |
Jun 25, 2008 |
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12159979 |
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11937870 |
Nov 9, 2007 |
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12145913 |
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PCT/US07/00981 |
Jan 12, 2007 |
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11937870 |
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11331466 |
Jan 13, 2006 |
7445590 |
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PCT/US07/00981 |
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Current U.S.
Class: |
493/370 |
Current CPC
Class: |
B31B 70/642 20170801;
B29C 66/8122 20130101; B29C 66/8122 20130101; B29C 66/91231
20130101; B29C 66/91212 20130101; B29C 66/81264 20130101; B29C
66/91651 20130101; B29K 2995/006 20130101; B29C 65/7471 20130101;
B29C 66/962 20130101; B29C 66/7352 20130101; B29C 66/81821
20130101; B29C 66/961 20130101; B31B 70/645 20170801; B29C 65/226
20130101; B29C 66/8181 20130101; B29C 66/1122 20130101; B29C 66/71
20130101; B31B 2155/00 20170801; B29C 65/222 20130101; B29C 66/3474
20130101; B29C 66/71 20130101; B29C 66/21 20130101; B29C 66/9241
20130101; B29C 66/939 20130101; B31B 2160/10 20170801; B29C 66/949
20130101; B29C 66/43 20130101; B29C 66/91315 20130101; B29K 2001/00
20130101; B31B 70/024 20170801; B31B 70/649 20170801; B31B 70/14
20170801; B29C 65/7433 20130101; B29C 66/81419 20130101; B29C
65/305 20130101; B29C 66/244 20130101; B29C 66/91421 20130101; B29C
66/81871 20130101; B29C 65/228 20130101; B29C 66/73791 20130101;
B29C 66/80 20130101; B29C 66/83433 20130101; B29C 66/9241 20130101;
B29K 2023/0625 20130101; B29C 65/1425 20130101; B29C 66/8167
20130101; B29C 66/82421 20130101; B29C 66/8244 20130101; B29C
66/8511 20130101; B29C 66/91641 20130101; B29C 66/91653 20130101;
B29K 2995/007 20130101; B29C 65/18 20130101; B29L 2031/7128
20130101; B29C 66/8122 20130101; B29C 66/91421 20130101; B29C
66/91423 20130101; B29C 66/91631 20130101; B29C 65/38 20130101;
B29C 59/007 20130101; B29C 66/71 20130101; B29C 66/71 20130101;
B29C 65/229 20130101; B29C 66/232 20130101; B29C 66/3472 20130101;
B29C 66/71 20130101; B29K 2003/00 20130101; B29C 65/00 20130101;
B29K 2827/18 20130101; B29K 2067/046 20130101; B29K 2001/00
20130101; B29K 2909/08 20130101; B29K 2023/0625 20130101; B29C
65/00 20130101; B29K 2003/00 20130101; B29C 65/14 20130101; B29C
66/83511 20130101; B29C 66/81455 20130101; B29C 66/919 20130101;
B29C 66/0044 20130101; B31B 70/16 20170801; B31B 70/64 20170801;
B29C 65/7437 20130101; B31B 70/00 20170801; B29C 66/93451 20130101;
B29C 2793/0045 20130101 |
Class at
Publication: |
493/370 |
International
Class: |
B31B 1/14 20060101
B31B001/14 |
Claims
1. A converting machine, comprising: an input section; a rotary
drum, disposed to receive a web from the input section, wherein the
rotary drum includes at least one seal die disposed thereon; an
output section, disposed to receive the web from the rotary drum;
and wherein the at least one seal die includes a weakening zone
that forms a perforation with an auxiliary sealed area about the
perforation.
2. The converting machine of claim 1, wherein the weakening zone
extends in the machine direction at least as far as it extends in
the cross machine direction.
3. The converting machine of claim 1, wherein the weakening zone
includes a heating wire.
4. The converting machine of claim 3, further comprising a release
layer on at least a part of the weakening zone.
5. The converting machine of claim 1, wherein the output section
includes a winder.
6. The converting machine of claim 5, wherein the output section
includes a rotary knife that receives the web from the rotary drum
and cuts the web to form the web into a plurality of converted
articles, and wherein the winder receives the plurality of articles
from the rotary knife.
7. The converting machine of claim 1, wherein the input section
includes at least one of an unwind module and an extruder.
8. A method of converting film into a plurality of articles,
comprising: feeding a film to a rotary drum; forming, on the film,
a plurality of perforations with auxiliary sealed areas about the
perforations using at least one seal die disposed on the rotary
drum; and forming a perforation between successive articles.
9. The method of claim 8, wherein forming includes forming the
perforations and auxiliary sealed areas such that the perforations
and auxiliary sealed areas extend in the machine direction at least
as far as they extends in the cross machine direction.
10. The method of claim 9, wherein the forming heating a wire.
11. The method of claim 10, further comprising winding the
successive articles.
12. The method machine of claim 11, further comprising cutting the
film with a rotary knife to form the film into a plurality of
converted articles prior to winding.
13. The method of claim 12, further comprising, prior to feeding,
at least one of an unwind the film and extruding the film.
14. A machine for converting film into a plurality of articles,
comprising: means for feeding a film to a rotary drum; means for
forming, on the film, a plurality of perforations with auxiliary
sealed areas about the perforations; and means for forming a
perforation between successive articles.
15. The machine of claim 14, wherein the means for forming includes
a heating a wire.
16. The machine of claim 14, further comprising means for winding
the successive articles, wherein the means for winding operates on
the successive articles after the means for forming operates on the
film.
17. The machine of claim 16, further comprising means for cutting
the film to form the film into a plurality of converted articles
prior to the means for winding operating on the film.
18. The machine of claim 14, wherein the means for feeding includes
at least one of an unwind and an extruder.
Description
RELATED APPLICATIONS
[0001] This is a continuation-in-part of, and claims the benefit of
the filing date of, U.S. patent application Ser. No. 13/042,870,
filed Mar. 8, 2011, entitled Method and Apparatus For Making
Skirtless Seals, which is a continuation of and claims the benefit
of the filing date of U.S. patent application Ser. No. 12/253,724,
filed Oct. 17, 2008, entitled METHOD AND APPARATUS FOR MAKING
SKIRTLESS SEALS and issued as U.S. Pat. No. 8,029,428 on Oct. 4,
2011, which is a continuation-in part of and claims the benefit of
the filing date of, U.S. patent application Ser. No. 12/159,979,
filed Jul. 2, 2008, entitled Method and Apparatus For Making Bags,
and is a continuation-in-part of, and claims the benefit of the
filing date of, U.S. patent application Ser. No. 12/145,913, filed
Jun. 25, 2008, entitled Method and Apparatus For Making Skirtless
Seals, which is a continuation-in-part of and claims the benefit of
the filing date of application Ser. No. 11/937,870, filed Nov. 9,
2007, entitled Rotary Bag Machine With Skirtless Seal, and which
claimed priority and the benefit of the filing date of PCT
Application No. PCT/US07/00981, filed Jan. 12, 2007, entitled
Method and Apparatus For Making Bags, and which is a
continuation-in-part of and claims the benefit of the filing date
of application Ser. No. 11/331,466, filed Jan. 13, 2006, and
entitled Method and Apparatus For Making Bags, which issued on Nov.
11, 2008, as U.S. Pat. No. 7,445,590.
FIELD OF THE INVENTION
[0002] The present invention relates generally to the art of
converting film by forming seals. More specifically, it relates to
machines and a method that create an article from a film or web by
forming seals and/or perforations or a line of weakness, and by
separating adjoining articles made from the film.
BACKGROUND OF THE INVENTION
[0003] There are many known bag machines. One style is a rotary
drum machine. Rotary drum machines are well known, and a detailed
description may be found in U.S. Pat. Nos. 6,117,058, 4,934,993,
5,518,559, 5,587,032 and 4,642,084 (each of which is hereby
incorporated by reference).
[0004] A detailed description of the operation of rotary bag
machines may be found in the patents above, but their general
operation may be seen with respect to FIG. 1. A prior art rotary
bag machine 100 continuously processes a film/web 201 using a
dancer assembly 203, a pair of drum-in rolls 205 and 206 (203-206
are part of an input section), a sealing drum 208, a pair of
drum-out rolls 210 and 211, a sealing blanket 213, a pair of
knife-in rolls 215 and 216, a knife 218 (which could be any other
web processing device such as a perforator, knife, die cutter,
punching station, or folding station), a pair of knife-out rolls
219 and 220 (210-220 are part of an output section), and a
controller 221. Input section, as used herein, includes the portion
of a bag machine where the web is received, such as an unwind and a
dancer assembly. Output section, as used herein, includes
assemblies that act on a web downstream of the seals being formed,
such as perforators, winders, folders, etc.
[0005] The web is provided through dancer assembly 203 to drum 208.
Drum 208 includes a plurality of seal bars 209. The seals bars are
heated and create the seals forming the bags from web 201. Web 201
is held against drum 208 (and the seals bars) by a Teflon.RTM.
coated blanket. The distance between seals created by the drum is
related to the bag length (for bags formed end to end) or the bag
width (for bags formed by making side seals). End to end bags are
formed with one seal from the drum, and side to side bags are
formed with a pair of seals. The drum diameter may be adjusted
and/or less than all of the seal bars turned on to determine the
distance between seals, and hence bag size.
[0006] The prior art of FIG. 1 provides that after web 201 leaves
drum 208 it is directed to rotary knife 218, which creates a
perforation between bags, or could separate adjoining bags. When
the bags are end to end bags the perforation is placed close to the
single seal such that when the bags are separated, the perforation
and the perforated end is the top of one bag, and the seal is the
bottom of the adjoining bag for end seals, or sides of adjacent
bags for side seals. Ideally, the perforation is close to the seal
to reduce waste, although this is difficult in practice. When bags
are formed side to side, the perforation is made between the pair
of seals. A seal is needed on both sides of the perforation, since
the side of both bags should be sealed. The web between the pair of
seals is wasted. Thus, the pair of seals should be close to one
another to reduce waste, although this is also difficult in
practice.
[0007] Controller 221 is connected to the various components to
control speed, position, etc. Sensors may be used to sense print on
the web to form the seals and/or register the perforation (place it
in the correct location with respect) to the seal. Also, sensors
may detect seals to try and create the perforation in the correct
location. Sensing the seal has proven to be difficult. One prior
art example of a system that sensed seals is described in U.S. Pa.
No. 6,792,807, hereby incorporated by reference. If the perforation
is placed too close to one side seal, then the seal may be cut off,
rendering the bag useless.
[0008] Because sensing the seal is difficult, waste is generated in
bag making, or bags are ruined. The wasted web, (i.e. the web
between a seal and the adjacent perforation), or the web used to
make the ruined bag, can be costly, particularly for high speed bag
machines where the number of bags made per hour is great.
[0009] Another problem of prior art machines is that perforations
may be skewed with respect to the seals, because the perforations
are created downstream, and the web can wander or stretch. Also, a
mechanical perforation knife must be adjusted every few days to
continue to perform properly. Generally, sharp mechanical knives
cannot be adjusted to change the perforation strength, and they can
be costly, complex, and difficult to use.
[0010] Other type of bag machines, such as intermittent motion
machines (not rotary drum machines) use burn off seals to seal and
cut or perforate at the same time but speed is limited to about 300
fpm due to the reciprocating motion, dwell time, and difficulty
handling the loose bags. Other intermittent motion machines, such
as the CMD Icon.TM., have seal bars with an integral toothed blade.
The CMD CM300.TM. machine has oscillating motion to move seal bars
that have an integral toothed blade. Generally, intermittent motion
machines are not as fast as rotary drum continuous machines, and
thus produce far fewer bags per machine hour.
[0011] Some prior art rotary drum bag machines create two parallel
seals, and a perforation therebetween as the film moves with the
drum. For example, U.S. Pat. No. 6,635,139 to Bohn, et al., and
prior related application US 2007-0167304, Selle et al., which
issued as U.S. Pat. No. 7445590 on Nov. 4, 2008, both of which are
hereby incorporated by reference.
[0012] These bag machines have been limited to forming bags.
Adapting this technology for converting film into other articles
using a continuous motion machine such as a rotary drum machine
would be desirable.
SUMMARY OF THE PRESENT INVENTION
[0013] A converting machine, according to a first aspect of the
invention, includes an input section, a rotary drum, and an output
section. The rotary drum receives the web from the input section
and there is at least one seal die disposed on the drum. The output
section receives the web from the rotary drum. The at least one
seal die has a weakening zone that forms a perforation with an
auxiliary sealed area about the perforation.
[0014] According to a second aspect of the invention a method of
converting film into a plurality of articles includes feeding a
film to a rotary drum, forming a plurality of perforations with
auxiliary sealed areas about the perforations, and forming a
perforation between successive articles.
[0015] The weakening zone extends in the machine direction at least
as far as it extends in the cross machine direction in one
embodiment.
[0016] The weakening zone includes a release layer in other
embodiments.
[0017] The output section includes a rotary knife and/or a winder
according to various embodiments.
[0018] The input section includes at least one of an unwind module
and an extruder in other embodiments.
[0019] Other principal features and advantages of the invention
will become apparent to those skilled in the art upon review of the
following drawings, the detailed description and the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is bag machine in accordance with the prior art;
[0021] FIG. 2 is rotary drum in accordance with the present
invention;
[0022] FIG. 3 is an end view of a seal bar in accordance with the
present invention;
[0023] FIG. 4 is a side view of a seal bar in accordance with the
present invention;
[0024] FIG. 5 is a top view of a segment of the seal bar of FIG.
3;
[0025] FIG. 6 is a top view of an insert/cap in accordance with the
present invention;
[0026] FIG. 7 is a side view of the insert of FIG. 6;
[0027] FIG. 8 is a seal and weakened zone in accordance with the
present invention;
[0028] FIG. 9 is an end view of a seal bar in accordance with the
present invention;
[0029] FIG. 10 is an end view of a seal bar in accordance with the
present invention;
[0030] FIG. 11 is an end view of a seal bar in accordance with the
present invention;
[0031] FIG. 12 is an end view of a seal bar in accordance with the
present invention;
[0032] FIG. 13 is an end view of a sealer/perforater in accordance
with the present invention;
[0033] FIG. 14 is a seal and weakened zone in accordance with the
present invention;
[0034] FIG. 15 is a perspective view of a segment of a seal bar in
accordance with the present invention;
[0035] FIG. 16 is a perspective view of a segment of a seal bar in
accordance with the present invention;
[0036] FIG. 17 is a top view of a portion of the segment of the
seal bar of FIG. 16; and
[0037] FIG. 18 is an end view of a cap that may by used with the
seal bar of FIGS. 16 and 17; and
[0038] FIG. 19 is a perspective view of a rotary drum with sealing
dies mounted thereon.
[0039] Before explaining at least one embodiment of the invention
in detail it is to be understood that the invention is not limited
in its application to the details of construction and the
arrangement of the components set forth in the following
description or illustrated in the drawings. The invention is
capable of other embodiments or of being practiced or carried out
in various ways. Also, it is to be understood that the phraseology
and terminology employed herein is for the purpose of description
and should not be regarded as limiting. Like reference numerals are
used to indicate like components.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0040] While the present invention will be illustrated with
reference to a particular bag machine, it should be understood at
the outset that the invention can also be implemented with other
machines, and using other components. Bag machine, as used herein,
includes a machine used to make bags such as draw tape bags,
non-draw tape bags, and other bags. Any input section (unwinds and
dancers, e.g.) and any output section (winders, folders, e.g.) may
be used with the present invention. Bags may be comprised of
traditional poly material, other materials such as starch,
polyactic acid (PLA), cellulose, polyhydroxy alkanoates (PHA), and
lignin, and/or be biodegradable, compostable, etc., such as
Mater-Bi.RTM., Ecoflex.RTM., Ecovio.RTM., Bioplast GF106.RTM.
[0041] Generally, one aspect of the present invention provides for
converting film or a web into a plurality of successive articles.
The conversion is performed, in one embodiment, using a plurality
of sealing dies mounted on a rotary drum instead of or with the
seal bars. This embodiment is described below with respect to FIG.
19.
[0042] Generally, the present invention provides for a rotary bag
machine with an input section, a drum section, and an output
section. A single seal is formed, and a perforation or line of
weakness is formed within the single seal, as the film moves with
the rotating drum. Thus the single seal, with the perforation
therewithin, forms seals for two adjacent bags.
[0043] Preferably, the single seal is created using a single
sealing zone. alternatively, the single sealed area can be created
using two seals that melt to form a single seal, or a single
sealing zone. In either case, the single seal is comprised of two
parallel sealing subzones, with a perforation or weakened area
within the single seal. Other sealing techniques may be used. The
single seal can be combined with other embodiments, such as hem or
draw tape seals, varying intensity seals and perforations, etc.
[0044] The seals and perforations can be formed for less than the
time the film is about the drum. For example, on a rotary bag
machine the web might be in contact with the drum for about
one-half of the drum cycle, and the perforation formed in one
quarter of the drum cycle. The seal bar includes a sealing zone and
applies heat as the drum rotates, thus forming the single seal.
[0045] Seal bars, as used herein, includes an assembly, such as on
a rotary drum, that applies heat to and seals the web, and the
mounting mechanisms, perforators, etc. Sealing zone, as used
herein, includes the portion of a seal bar that creates the seal.
Within the sealing zone, as used herein, includes, within the
boundaries of a single sealing zone. Within a single seal, as used
herein, includes, within the boundaries of a single seal. Single
seal, as used herein, includes, an area of film that is melted to
form a seal without unsealed portions that extend a substantial
distance in the cross machine direction. A single seal may have
small gaps in the seal, either intentionally or inadvertently, and
may have one or more subzones.
[0046] The seal bars can have independently controlled cross
machine temperature zones, for example for applying more heat to a
hem or draw tape portion of a side seal. Independently controlled
temperature zones, as used herein, includes temperature zones along
a sealing zone that can be controlled or caused to be different
temperatures.
[0047] A perforator or weakening zone is mounted within the single
sealing area, and may be part of a cap or insert. The weakening
zone creates a perforation or weakened area as the seal is being
formed. The perforation can be created with heat, radiation, or by
mechanical contact. Weakening zone, as used herein, includes the
portion of a seal bar that creates a weakened area. Weakened area,
as used herein, includes an area on the web which is weakened, such
as by a perforation or a portion of the web being melted or burned
off.
[0048] The cap can alternatively include a separating zone for
separating adjoining bags. This typically requires more heat than
weakening or perforating. Separating zone, as used herein, includes
the portion of a seal bar that separates adjoining bags. One
embodiment provides for retrofitting existing machines by placing a
cap or insert on existing seal bars, or by replacing seal bars with
seal bars designed to have a weakening zone, such as with an
insert.
[0049] Thus, the perforation is located consistently and correctly
within the single seal that forms the sides of adjacent bags. Less
film is wasted because the distance between the pair of side seals
is less. While typical prior bag machines have one inch between
side seals, the preferred embodiment creates a single seal about
0.65 inches across that is the seal for two adjacent bags. Thus,
each bag has a side seal of about 0.325 inches, with no space
between the seal and the edge of the bag. About, as used herein,
includes a magnitude being close enough to a given value to
function substantially the same as if the magnitude were the given
value.
[0050] A wide variety of perforators can be used, such as a heating
wire, heat film, toothed blades, etc. Heat film, as used herein,
includes a film used to apply heat to a specific area. The
perforation strength may be adjusted by controlling the amount of
heat (or pressure) applied at the perforator. The perforation may
be clearly defined, a line of weakness, or a line of weakness that
varies in intensity. Line of weakness that varies in intensity, as
used herein, includes varying web strength along a line or curve,
such as a perforation or such as a line where the web is not
removed, but alternates between low and higher strength
regions.
[0051] The heated perforator may include a wire in intermittent
contact with the web, to create the perforation pattern.
Intermittent contact between the web and a sealing or perforating
element, as used herein, includes the web being in contact with the
element at some locations and not in contact at other locations,
such as contact and no contact alternations along a cross-machine
direction line.
[0052] Heated perforator, as used herein, includes a device that
uses thermal energy to perforate, through contact, convection,
conduction or radiative heat. Heating wire, as used herein, is a
wire used to heat, such as by passing electrical current
therethrough. Radiative heat, as used herein, includes heat in the
form of electromagnetic radiation, ultrasonic radiation, thermal
radiation, etc.
[0053] The blanket may be blankets such as those found in the prior
art, although the preferred embodiment includes a blanket that is a
belt consisting of 2-ply polyester material with 1/32'' ground
silicone top cover Silam K.RTM. (55 durometer) with an endless
length. Other blankets, preferably able to handle the high
intermittent temperatures (600-800 F) that can be reached while
burning a perforation and that have good release characteristics so
the film does not stick to the belting, are contemplated in various
embodiments, and may be Teflon.RTM., silicon, hybrids, etc. Another
embodiment uses a fine fabric mesh impression in the silicon
surface of the blanket. This results in an impression made in the
film that can aid in sealing or perforating and also improve the
release characteristics. One embodiment provides for the blanket to
have a 0.03-0.012 in. thick silicone rubber top surface with a
matte finish, durometer 50-90 Shore A, initially seasoned with a
talc powder. Another embodiment uses the fine fabric impression
(bumpy or textured) blanket, such as a Habasit.RTM. WVT-136 silcone
rubber blanket, such that the pressure of the "bumps" burns through
the plastic to form the weakened zone.
[0054] Turning now to FIG. 2, a drum 200 consistent with the
present invention is shown. Drum 200 includes four seal bars 229,
and a blanket 230 that holds a web or film against drum 200 and
seal bars 229. Drum 200 operates generally as the prior art drum,
but seal bars 229 include a perforator.
[0055] Drum 200 is preferably one similar to the CMD 1270GDS Global
Drawtape System.RTM. and has approximately 0.5 seconds of seal
dwell time at 600 fpm and has an adjustable diameter to easily
change product repeat lengths. It has 4 seal bars equally spaced
around the circumference that span across a 50'' web width. This
drum can be used for making trash can liners or garbage bags, for
example. Other drums could consist of more or less seal bars,
larger or smaller diameter, or narrower or wider web widths.
[0056] Referring now to FIG. 3, an end view of a seal bar 300 in
accordance with the preferred embodiment is shown. Seal bar 300
includes a cap 301 and portions 303 and 305. A heater cartridge 307
is preferably disposed in split bar portions 303 and 305, to allow
for easy replacement of cartridge 307.
[0057] Cap 301 is preferably 0.65 inches wide to form a single seal
of that width. Two pieces of kapton tape 310 and 311 (each 0.003
inches thick) are taped to cap 301, centered in the machine
direction. A perforating wire 312 is mounted on cap 301 (by
stitching into cap 301 in the preferred embodiment), over tapes 310
and 311. Tapes 310 and 311 are provided to place perforating wire
312 at a desirable height for obtaining the necessary pressure (of
the film between wire 312 and the blanket) for creating the
perforation. Tapes 310 and 311 are of different widths, so as to
provide a more gradual transition from the cap height to the wire
height. This helps the uniformity and integrity of the single seal
created by seal bar 300. Tape 311 is 0.25 inches across, and tape
310 is 0.38 inches across in the preferred embodiment. Tapes 310
and 311 are preferably comprised of kapton, to obtain a desired
release and wear balance (there is often a trade off between better
release of the film vs. greater wear of the tape).
[0058] A pair of teflon tapes 314 and 315 are provided over the
surface of cap 301, and over tapes 310 and 311, to help release the
film and to help create a uniform single seal. Tapes 314 and 315
are preferably 0.002 inches thick.
[0059] Seal bar 300 preferably has a uniform temperature range
across a given width of a web, with an independently controlled
temperature zone at the edge for making a side seal while
simultaneously making a tape seal with bar 401.
[0060] Wire 312 is preferably NiCr and may be connected to a DC or
AC power supply, and can be comprised of multiple wires, such as
for providing more heat to the drawtape area. Multiple wires can be
separate wires with separate power supplies, parallel wires, or
series segments of a wire. Power to the wire may be on constantly,
pulsed on and off, or have an otherwise varying power level. Proper
timing of the pulses allows the seals to cool prior to where the
web leaves the drum, for easier separation of the web from the seal
bar.
[0061] NiCr wire 312 is stitched into cap 301 such that wire 312
has intermittent contact with the web (such as areas of contact
where film is burned away, and areas of no contact where film is
not burned away to create perforation tabs). NiCr wire 312 is
preferably pulsed on for the first half of the dwell time (the time
the web is against the seal bar) and allowed to cool the second
half of the dwell time so the perforations are non-molten when the
web separates from the perforator. This allows a stronger web,
reduces film sticking to the wire, and eliminates the chance of the
perforation melting shut.
[0062] Cartridge heater 307 is a custom wound heat zone such as
those available from Watlow.RTM. or Thermal Corp. in the preferred
embodiment. The temperature profile for specific or different
temperature setting combinations (desirable especially on thin
films) may be controlled using compressed air cooling of hot zones,
as described below. Air cooling is also used for isolating
different temperature zones which are located next to each other
but are set at greatly different temperatures such as 300 F (bar
304) for side seals but 450 F (bar 401) for tape seals, in various
embodiments.
[0063] Referring now to FIG. 4, a side view of seal bar 300 is
shown. Seal bar 300 includes, in the preferred embodiment, a first
temperature zone 401 for a draw tape seal (or for a hem) and a
second temperature 402 for making a side seal. Temperature zone 402
may include multiple temperature zones 403, 404 and 405.
[0064] Turning now to FIG. 5 a top view of end cap 301 of seal bar
300 of FIG. 3 is shown and produces a single seal, with a
perforation or weakened area within the seal. Seal bar 300 may be a
generally known seal bar, with the changes described herein. Seal
bar 300 is preferably an aluminum bar with a firerod cartridge
heater mounted inside, and includes a sealing cap 301 that forms a
single seal. Tapes 314 and 315 are release layers disposed on the
top of cap 301, to allow the film to release after the seal is
formed. The portion of cap 301 shown forms a single seal in a draw
tape region of the film or web. A similar portion forms the seal in
the non-draw tape area.
[0065] The single seal created may have a non-uniform intensity but
has sufficient strength throughout to be a single seal with
sufficient integrity for the intended use of the bag. Release
layers 314 and 315 are preferably Teflon.RTM. tape, but
alternatives provide for the release material to be Rulon.RTM.
tape, Kapton.RTM. tape, Mica.RTM. tape, Resbond.RTM. painting,
Rescor.RTM. paint, and/or RP Polyimide resin poured and baked onto
the surface (available from Unitech in VA). One embodiment omits
the release layers. Release layers 314 and 315 extends over the
side areas adjacent (and outside) the sealing zone in one
embodiment (FIG. 3), and do not in another embodiment. Release
layers 314 and 315 extend nearly to wire 312 in one embodiment (as
shown by the solid lines 314A 315A), and do not extend nearly to
wire 312 in other embodiments.
[0066] The single sealing zone (the top of cap 301) extends under
release layers 314 and 315, and under wire 312. Tape 310 is placed
over cap 301, and thus is under tapes 314 and 315 except near wire
312. Because tape 310 is not seen from the top view of FIG. 5, the
edges 310A of tape/release layer 310 are shown as dashed. Tape 311
is placed over tape 310, and is under tapes 314 and 315 except near
wire 312. Thus tape 311 can be a release layer, particularly near
wire 312. The edges 311A of tape/release layer 311 are shown as
dashed because they are not visible in the top view of FIG. 5.
Tapes 310 and 311 are preferably Kapton.RTM. tape, but could be
Teflon.RTM. tape, Rulon.RTM. tape, Mica.RTM. tape, Resbond.RTM.
painting, Rescor.RTM. paint, RP Polyimide resin poured and baked
onto the surface (available from Unitech in VA), and/or other
non-stick materials. Tapes 310 and 311 may be omitted, or
additional tapes used, in various embodiments, depending on the
desired height of wire 312, for intended applications. Wire 312 is
placed at the desired height using methods other than tape, such as
by a rounded or raised cap 301, a thin metal plate, etc., in
various embodiments.
[0067] An electrically insulating coating is preferably used if
seal bar 300 and/or cap 301 are aluminum, to prevent shorting of
wire 312. If an insert (described below) is used, and the insert is
conductive, the insulating coating is used with the insert.
Alternatively, the insert could be made of a non-conductive
material.
[0068] Heating wire 312, preferably NiCr, is disposed within the
draw tape area. Heating wire 312 is stitched into single sealing
zone/cap 301, and is also stitched through tapes 310 and 311.
Alternatively, wire 312 may be stitched into an insert such as
those shown below. Cap 301 is preferably used to make replacement
easier--rather than replacing an entire heater, or re-applying the
release layer and re-stitching a wire, only a new cap with release
layers and wire need be applied to the heater. The used cap can be
refurbished. Stitched into the sealing zone, as used herein means
the wire is placed in holes in the material in which it is mounted,
thereby creating an area where the web is not melted away, such as
the solid portion between holes in a perforation.
[0069] The ratio of the perforator wire 312 height to the seal area
width (the width of cap 301) should be selected to obtain good
perforations and good seals at the same time for a given
application, and can be different for the draw tape area relative
to the rest of the seal. When making a single seal 0.65 inches
wide, the height of wire 312 can be between 0.015 and 0.025 inches
taller than the top of cap 301 in some applications.
[0070] Wire 312 terminates at a silver or sliver coated pin
(preferably 0.125 inches diameter and 0.75 inches long). A copper
wire from the power supply is crimped to the silver pin, thereby
connecting wire 312 to the power supply. A similar arrangement is
provided for in the non-draw tape region, with cap 301, tapes 310,
311, 314 and 315, and wire 312. Cap 301 may be one continuous cap,
or more than one cap extending across the web. The draw tape region
has heating wire 312 and the sealing zone raised so that extra
pressure is applied, and thus more melting occurs, in the draw tape
area. Alternatively only one of, or neither of, the perforating
zone and sealing zone can be raised. A draw tape area is raised
relative to the remainder of the sealing zone when the draw tape
area projects closer to the sealing blanket, thus resulting in
greater pressure in the draw tape area. Alternatively, a rubber
wheel or auxiliary belt may press against the back of the sealing
blanket to increase pressure in the drawtape area.
[0071] Heating wire 312 is preferably 80% nickel and about 20%
chromium, and/or a thin film heater, and/or a resistance heater,
and/or disposed to be make intermittent contact with the web,
and/or has a resistance of about 4 ohms/ft, and/or disposed in an
insert and/or cartridge on the seal bar in various embodiments. The
stitching can ne that described below with respect to other
embodiments.
[0072] The surface of cap 301 may be arcuate shaped to help create
greater pressure throughout the draw tape seal region and thus to
transfer more heat and make a satisfactory seal through the extra
layers of film present in the draw tape hem. Arcuate shape, as used
herein, includes a surface that curves rather than a straight
surface, and thus an arcuate sealing surface has a different
pressure profile than a straight sealing surface. Alternatives
provide for an arcuate shape throughout the entire seal region, or
other profiles, including flat.
[0073] One alternative embodiment provides for seal bars that form
side seals only, with no drawtape seal zone. Cartridge heater 307
is replaced with a flexible silicone rubber heater in another
embodiment. The heaters may be held on the sides of an aluminum bar
using pressure sensitive adhesive (available from Watlow.RTM.).
[0074] Another embodiment of the invention includes an insert 2600,
or in other embodiments a cap 2600, as shown in FIG. 5, and
includes a separate heat zone 2601, such as for heating a hem or
draw tape region. Cap/insert 2600 is mounted on a seal bar. Insert,
as used herein with reference to a seal bar, includes an assembly
mounted on or with the seal bar that is in addition to the sealing
zone that creates the seal or seals. Cap, as used herein with
reference to a seal bar, includes an assembly that forms the upper
part of a seal bar, which is heated to form the seal or seals.
[0075] Various embodiments provide for region 2601 to be used with
or without a perforation that extends across the film (the
perforation could cross a drawtape, and the seal could extend the
width of the film, e.g.). Within region 2601, a 0.020 in. mica
layer (or a Glastherm HT.RTM. layer) 2603 is provided. A NiCr wire
is disposed in a series of cavities or holes (as in FIG. 16). The
holes are located every 0.312 inches, and have a 0.030 in. diameter
in region 2601. The insert is 0.25 inches wide, and the seals
(between which the perforation is made) are 0.25 inches apart.
[0076] The side view of insert 2600, shown in FIG. 7, shows a NiCr
wire 2701 disposed in the holes in region 2601. The wire preferably
has a 0.0089 in. diameter in region 2601. Wire 2701 is serially
connected to a 0.0126 NiCr wire 2703 (using a crimp 2705). The
larger wire requires larger holes (0.062 in. in the preferred
embodiment). The wire sizes can be chosen to select the wire
resistance, and thus the heat provided. Wire 2703 is soldered to
and/or wrapped around a preferably silver pin to be connected to a
high temperature wire 2707 with a crimp connection. A release layer
may be placed over the wire or between the wire and insert base.
Release material may include: Teflon.RTM. tape, Rulon.RTM. tape,
Kapton.RTM. tape, Mica.RTM. tape, Resbond.RTM. painting, and
Rescor.RTM. paint. Release layer, as used herein, includes the
surface os a seal bar or perforator that has a coating or layer of
material that has properties that help prevent melted film from
sticking to the surface, and is on or adjacent the surface that
touches the film when the seal or perforation is being created.
[0077] The NiCr wire may be turned on and off (current flow) to
control temperature of the wire/sealing. For example, the wire may
be turned on immediately after contacting the film (or blanket),
and turned off immediately after the contact with the film (or
blanket) ends. Alternatives include connections other than serial
between wires 2701 and 2703, more heat zones (and wire
connections/types), controlling heat with external
resistors/potentiometers or current magnitude, such as with PWM. If
a pot is used the user could adjust the relative temperature by
adjusting the pot. Other embodiments includes combining these
features, or other on/off schemes. This and other embodiments may
be used with any other bag where a perforation needs to be placed
next to a seal, such as t-shirt bags, including reinforced t-shirt
bags, draw tape bags, side seal bags, etc. The wire may be off for
part of the time the seal is being made and on for at least a
portion of the time the first seal is being formed. One embodiment
calls for preheating the wire when it is not in contact with the
film so it is turned off while in contact with the film, relying on
the wires retained heat to burn the perforations.
[0078] The wire may be held in the holes using a Resbond.RTM. high
temperature adhesive, injected into the holes using a syringe. Hard
or flexible adhesives, or both, alternating, e.g.) may be used.
Flexible adhesives allow the wire to flex, which can occur when it
is heated and cooled. The insert may be held in place with five
cone point set screws 2605 or with flat tip set screws.
[0079] Other alternatives provide for wire 1502 to be round, a
rectangular ribbon, straight or woven at a uniform or varying
pitch, uniform thickness or non-uniform thickness along their
length (to create hot/cold spots), Toss.RTM. wire, tapered, or
profiled to make two side seals between a burn off cut. Profiled
wire may have intermittent copper plating to perforate rather than
clean cut. Varying pitch for a woven wire or different hole spacing
creates a weakened area of varying weakness, that allows the bag to
be torn by hand easier at the edge than in the middle of the web.
Other designs contemplated include flexible silicone rubber
heaters, thick film heating technology, sintered ceramic, or the
like available from Watlow Electric Manufacturing Co. Yet other
alternatives include using thin film heating technology mounted on
a PNEUSEAL.TM. rubber inflatable diaphragm that can stay hot all
the time but physically move in and out of contact with the film by
inflating and deflating the diaphragm.
[0080] The preferred embodiment controls the heat of a burn-perf
wire by controlling an AC voltage. AC is preferred for cost,
although DC voltage control may provide better control. Preferably
the lowest voltage that provides an acceptable perforation is used.
For example, a 0.013'' diameter 80/20 Ni--Cr wire woven alternating
between 0.25 inch in contact with the web and 0.12 inches below the
mica requires approximately 20 watts per inch of web width to burn
perforations in 0.75 mil LLDPE film two layers thick at 600 feet
per minute. Thus, a 2 inch long perforator would use 10 volts
pulsed on for about 0.25 seconds as soon as the film is sandwiched
between the perforator and the seal blanket. With a 0.5 second
dwell time, the perforation has about 0.25 seconds to cool. The
preferred embodiment thus allows the perforation to be quickly
heated and cool down. The adjustable voltage is supplied by a DC
motor controller in one embodiment. Other embodiments includes a
mechanical rheostat, potentiometer, or adjustable resistor. An
adjustable AC voltage can preferably be used.
[0081] A controller may be used to compensate for resistance
changes over the life of the wire. For example, a Toss.RTM.
controller has current sensing feedback and adjusts voltage
accordingly to maintain a more consistent temperature. Cartridge
heaters may be controlled with thermocouple feedback using PID
temperature control, as is well known in the industry.
[0082] Other embodiments provide for making a vented bag, such as a
leaf bag. A vented leaf bag may only require seals 3401 around each
perforation 3403, without a continuous seal, as shown in FIG. 14.
The single seal/perforation may be created using a contoured seal
bar, and/or previous embodiments with the temperature controlled to
burn through in places.
[0083] The single seal may also be created using one seal bar, or
two disposed such that the two seals blend together to form a
single seal (i.e., no unsealed web between them) comprised of two
sub-seals. The sub seals are generally parallel and extend across
the web or film in the cross machine direction, and a weakened area
is formed between the generally parallel sub-seals. The perforation
may be made using any of the alternatives described above. Another
embodiment provides for using one of the embodiments above, but is
used by turning the side seal temperature very low so that the
seals are not formed. The perforator then forms the perforation and
the seals are the auxiliary seals from the perforation.
[0084] Referring to FIG. 9, one embodiment of a seal bar 2900 that
includes a single sealing zone and a weakening zone disposed within
the single sealing zone is shown. The single seal, with the
perforation formed therein, preferably extends at most 0.25 inches
in the machine direction, or more preferably at most 0.125 inches
in the machine direction on film 2912 after the seal and
perforation have been formed. Extending in the machine direction,
as used herein, includes the average distance over a portion of a
seal along lines running parallel to the film edge.
[0085] Seal bar 2900 forms a single seal on a web or film 2912. A
cartridge heater 2901 disposed within an aluminum block 2903
provides steady heat to seal bar 2900. Wire or resistance heater
2911 provides additional heat that creates the seal and weakened
area. Wire 2911 is preferably a NiCr wire 0.009-0.013 inches in
diameter. The different sources of heat combine so that both add
heat to the seal zone and the weakening zone, although in this
embodiment wire 2911 primarily provides heat for the weakening
area, and heater 2901 primarily can be thought of preheating the
assembly.
[0086] Alternatives provide for a flat or other shaped resistance
wire. The flat wire can have a raised ridge or be curved to form
the weakening zone, with cutouts where the solid portions between
perforation holes are located. Air under the bend can act as an
insulator to affect the heat profile of the ribbon.
[0087] A shim 2905 can be used, particularly for retrofits, to
force wire 2911 into tighter contact with web 2912. Other
embodiments call for greater shimming in the hem or draw tape area
(of about 0.020 inches in one embodiment), so the web in that area
is under greater pressure than the remaining portion of the film,
thus providing greater heat transfer for this region, or no shim at
all. Another embodiment provides for a backing wheel behind the
blanket in a hem or draw tape region that forces the blanket
against the web and provides greater pressure in that region.
[0088] An insert 2907 is preferably comprised of, or coated with,
an electrical or thermal insulating material to insulate wire 2911.
In various embodiments insert 2907, or the electrical insulating
material, is comprised of mica, glastherm, fiberglass phenolic,
plastics, polymers, aluminum (with an electrically insulating
coating) or other materials. Glastherm.TM., as used herein,
includes, a composite material of glass fibers and heat resistant
thermosetting resins
[0089] A releasing layer 2909 is disposed over insert 2907, and is
preferably comprised of teflon.RTM., rulon.RTM., or kapton.RTM.
tape. The releasing layer or releaser is chosen to be of a material
that releases melted film, but able to withstand the temperatures
needed to seal and perforate the film. Releasing layer on a seal
bar or insert, as used herein, includes, a layer that, compared to
other materials of the seal bar or insert, reduces the buildup of
melted film on the seal bar or insert. This embodiment provides
that the film touches only the wire and tape (over the insert),
although other embodiments provide that the film touches the insert
directly, and/or touches the aluminum block heater. Alternatives
provide for coating the wire with a releaser instead of or in
combination with the releasing layer. The release maybe an
application of a liquid layer that later dries such as
Resbond.RTM., Rescor.RTM., Teflon.RTM. paint, silicone paint, or
the like.
[0090] The single seal can extend across the entire film width, or
across part of the film with two seals used in one region, such as
a hem or draw tape region. The two seals may be formed as described
above. Another embodiment provides for two sub seals to be used
only in the draw tape area, and a single seal without sub seals
formed elsewhere or vice versa.
[0091] The selection of various materials, such as the releaser,
insulater, heater, wire, etc., is should be made in consideration
of the film thickness, the temperatures desired for perforating (up
to 600 F or more in one embodiment) and sealing the major portion
of the film and any hem or draw tape region, and the ability of the
sealing surface to release melted film. Improper selection could
result in premature wear of the material, or premature buildup of
melted film on the sealing surface. Alternatives provide for
turning on the wire earlier to preheat it, so it can be turned off
sooner, removing the built up film during the time the film is not
in contact with the seal bar by, for example, mechanical action,
heating, brush, or air blast, etc.
[0092] Other design concerns include the range of types and
thicknesses of films that will be used with the machine, heat
migrating between the hem and other regions, the perforation and
the seal, blanket material, dwell time, removing or addressing
wrinkles in the film, ink from the web building up on the sealing
surface, and providing different pressure zones.
[0093] Referring to FIG. 11, another embodiment of a seal bar 3000
that includes a single sealing zone and a weakening zone disposed
within the single sealing zone is shown. The general description of
the seals formed, and design considerations above, apply to this
and other embodiments. A wire or resistance heater 3003 mounted on
an aluminum heater 3001 creates the seal and weakened area. Mounted
on, as used herein, includes directly in contact with, or with
other layers or items disposed there between. Heater 3001 may be a
support bar rather than a heater. Wire 3003 may be as described
above, and a releaser may be provided under wire 3003, over wire
3003, or wire 3003 may be coated, if needed. Wire 3003 is
preferably a NiCr wire stitched into an aluminum bar with an
electrically insulative coating and/or the wire is coated with an
electrical insulator. Preferably, the wire is coated with a
releaser (which may also be the insulator)
[0094] Referring to FIG. 11, another embodiment of a seal bar 3100
is similar to seal bar 3000, but heat is provided by a thin film
heater 3103 in addition to a wire 3103 and a support bar or heater
3101, to create the seal and weakened area on a web 2912.
[0095] Referring to FIG. 12, another embodiment of a seal bar 3200
is similar to seal bar 3100, but an insulator 3202 is provided
between a thin film heater 3203 in addition to a wire 3207 and a
support bar or heater 3201, to create the seal and weakened area on
web 2912.
[0096] Referring to FIG. 13, a schematic of a single
sealer/perforator 3300 comprises a strip that may be affixed to a
seal bar or a seal bar insert. Sealer 3300 is easily replaceable,
and thus useful for applications where film builds up on the
sealer. Sealer 3300 includes a NiCr wire 3301 (which may be similar
to wires described above), a releaser 3303 that is also preferably
an electrical insulator and may be similar to the releasers
described above, a thermal or heat conducting layer 3305,
preferably comprised of aluminum to spread the heat created by a
resistance trace heater 3307, all of which is mounted to two sided
tape 3309. Thus, tape 3309 can be affixed to the top of an insert
for use on a support bar or seal bar, or taped directly to the seal
bar.
[0097] One modification of this embodiment provides for the
releaser to be a tape placed over the wire, and there may or may
not be holes or slits on the releaser aligned with the locations
where the perforations holes are to be made, so that the wire
contacts the film in these locations.
[0098] Referring not to FIG. 15, a perspective view of a seal bar
insert 3500 is shown, and includes heated aluminum block 3501, with
the a heater cartridge 3502. A plurality of pins 3503 extend
through the seal bar and create a micro perforation. Pins 3503 are
disposed in holes in block 3501 that are disposed at an angle to
avoid cartridge 3502. Pins 3503 may be conductive and connected to
a wire 3504 to heat pins 3503 to aid in perforating and//or
sealing. This embodiment, and the other alternative embodiment may
be combined as desired. For example, pins 3503 may be used with a
vacuum through the holes holding pins 3503, and/or they may be
combined with one of the many ways of creating the seal and
perforations described above on a single seal bar, where the micro
perforations aide in creating the weakened zone, or pins 3503 may
be the sole manner of forming the perforation.
[0099] The row of pins or needles are in an unheated or heated seal
bar and press against a Kevlar.RTM. sealing blanket material, which
will be less likely to be damaged from the sharp pins penetrating
into it, in another alternative. The rows of pins or needles could
be placed in blanket, and be held in phase with seal bars on the
drum, to create the perforation. Similarly, thin film heaters
and/or pins on a belt or blanket can press against a simple drum
face. No drum would be required if pressure is applied by the belts
against one another, such as by an elliptical shaped belt path for
both belts.
[0100] Another embodiment provides for the seal and perforation to
be formed using magnetic fields or inductive heat. A magnet
(permanent or electric) on the seal bar, with metal in the backing
blanket causes extra pressure in the perforation area to melt holes
where desired and less pressure in the sealing area. The magnetic
fields can be created to be disposed in a line across the film.
[0101] Another embodiment provides for the seal and perforation to
be formed together on a non-circular loop, such as an oval or
oblong, or on a shuttle machine. generally, the invention of these
embodiments call for the creation of a seal when and where a
perforation is created.
[0102] Other methods of perforating and sealing at the same time in
a rotary drum to preferably create a perforation down the middle of
one narrow seal are included withing this invention. For example,
three staggered rows of NiCr wire stitches may be used where the
outer two rows create the seals and the inner row creates the
perforation. Inner refers to the inner in the machine
direction.
[0103] One seal may be made with one rounded seal tip when the film
is under tension such that the center of the seal
thins/weakens/perforates during the sealing process. The seal bar
may have a bumpy surface at the crest to create the
perforations.
[0104] A seal bar may comprise a resistive coating placed over a
shaped electrically non-conductive material so the heat is
generated at exactly the sealing surface where it is needed and a
complex shape with various sealing heights can be achieved. This
could be done adapting thin film heater technology.
[0105] Another embodiment calls for increase sealing blanket
pressure, such as by factor of 5, 10 or 20, preferably 10, so the
burn-perforation temperatures can be lowered from 550 F-600 F to a
lower temperature where a wider variety of coatings and materials
are available (many materials have a 500 F maximum operating
temperature).
[0106] Yet another embodiment provides for a sealing bar comprising
two parallel heated strips that separate 0.03'' to 0.06'' during
sealing to stretch the film into a line of weakness or perforations
between the two strips.
[0107] Film could be tucked into a 1/8'' deep recess in the drum
seal bar such that perforations can be cut or burned below the
surface of the drum without damaging the sealing blanket. The
tucking can be mechanical or vacuum assisted.
[0108] Other methods of creating the seal and perforation could be
used, such as using radiant heat, microwaves, or light waves tuned
to especially heat and perforate the web. Hot glue could be
applied, or a liquid from inside drum such that it heat seals the
two poly webs together. The perforations could be done
simultaneously if hot liquid burns perforation holes at the same
time. A hot solid such as sand or poly pellet, or a hot liquid,
such as oil, could be forced through web such that it perforates
the web while forming a seal at the same time. Or the web could be
chemically treated to react with an additive such that film melts
together and melts perforation holes where excess chemical is
applied. Another alternative includes applying a time activated
acid in the drum which allows the web (non-sealed and
non-perforated) to be wound and placed inside a carton; then the
time activated acid creates a burn-off seal so the web later
becomes multiple sealed/separated bags.
[0109] The web could be sealed with conductive heat sealing, and
before the dwell time is over the web could be cryogenically frozen
in a perforation pattern such that the film fractures at each
perforation spot when it is flexed downstream.
[0110] Turning now to FIGS. 16 (perspective view of a seal bar), 17
(top view) and 18 (end view of a cap), an embodiment of the
invention that produces a single seal, with a perforation or
weakened area within the seal is shown. A seal bar 3600 may be a
generally known seal bar, with the changes described herein. Seal
bar 3600 is preferably an aluminum bar with a firerod cartridge
heater mounted inside, and includes a single sealing area 3602
under a release layer 3603 that forms a single seal in a draw tape
region of a web.
[0111] Another single sealing area 3612 under a release layer 3613
forms a single seal across the remainder of the web (the non-draw
tape area). The single seal created may have a non-uniform
intensity but has sufficient strength throughout to be a single
seal with sufficient integrity. Release layers 3603 and 3613 are
preferably Teflon.RTM. tape. Single sealing zone 3602 extends under
release layers 3603, and under a release layer 3605. Release layer
3605, with a perforator/heating wire 3607 create a perforation or
weakened zone in the draw tape region of the web. Release layer
3605 is preferably Kapton.RTM. tape. The alternatives described
above may be used with this embodiment.
[0112] A heating wire 3607, preferably NiCr, is disposed withing
the draw tape area. Heating wire 3607 is stitched into single
sealing zone 3602, and is also stitched through release layer 3605.
Alternatively, wire 3607 may be stitched into a cap 3801 (FIG. 18)
made of aluminum or another type of material.
[0113] FIG. 18 shows an end view of cap 3801, with release layers
3603 and 3605 on it, and wire 3607 is shown stitched into cap 3801
and release layer 3605. Cap 3801 extends across less than the
entire sealing sealing zone 3603 in another embodiment. Wire 3607
is mounted on top of cap 3801.
[0114] The various alternatives may be combined as desired, to
design a bag machine suited to a specific need.
[0115] FIG. 19 shows an embodiment where a plurality of successive
articles may be formed. the successive articles can be, in addition
to bags, things such as dentist chair covers, gloves, raincoats,
and other objects made from a film or web. Generally, this
embodiment provides that at least one sealing die is mounted on the
drum. the number of dies can be chosen based on the die size,
and/or the number of seal bars.
[0116] One embodiment provides that the film is converted into
covers for dental chairs. Preferably, the die forms a perforation
with auxiliary sealed areas around the perforation holes.
Alternatives provide for creating a seal and perforation, or just a
seal. This can be done with a heating wire or as otherwise
described above. A downstream rotary knife, or the seal bars
described above, can be used to form perforations between articles.
The formed articles can be wound on a winder downstream of the
rotary drum, and downstream of the rotary knife if one is used.
Other knifes could also be used.
[0117] Turning now to FIG. 19, a drum 208 in accordance with this
embodiment includes a plurality of sealing dies 1901 mounted on
drum 208 over seal bars 229. Seal bars 229 can be omitted, and
sealing dies 1901 can be mounted to whatever mechanism seal bars
229 are typically mounted. Each die 1901 includes a pattern 1903
(in this embodiment a dental chair cover). The pattern extends
substantially in the machine direction, preferably at least as far
in the machine direction as in the cross direction. Some die
pattern will each make multiple articles, such as gloves. The
collective length of the multiple articles is what determines the
length the pattern extends in the cross and machine directions
(rather than the length of one article). A teflon blanket can be
used to hold the film against the sealing pattern (also called
perforation pattern and weakening zone), as described above.
[0118] Input section 201 (FIG. 1) includes one or both of an
extruder or unwind, in various embodiments. The rotary knife can be
a knife 218 (FIG. 1), such as that used in the prior art. Rolls 219
and 220 can provide the film to a winder where the articles are
wound. Knife 218 can perforate between every article (such as for
large articles like a chair cover), or between groups of articles,
and can cut more than once per pattern.
[0119] The various alternatives may be combined as desired, to
design a film converter suited to a specific need.
[0120] Numerous modifications may be made to the present invention
which still fall within the intended scope hereof. Thus, it should
be apparent that there has been provided in accordance with the
present invention a method and apparatus for making bags that fully
satisfies the objectives and advantages set forth above. Although
the invention has been described in conjunction with specific
embodiments thereof, it is evident that many alternatives,
modifications and variations will be apparent to those skilled in
the art. Accordingly, it is intended to embrace all such
alternatives, modifications and variations that fall within the
spirit and broad scope of the appended claims.
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